The present invention relates to a glare protection device.
Glare protection devices of this type have long been known to the expert in the art. These devices encompass essentially a filter arrangement with at least one liquid crystal cell, at least one polarizer and one analyzer, as well as various passive light filters, especially IR- and UV- reflective filters. The liquid crystal cell is actuated by an optical-electrical transducer serving as feed current source, and the operating signal for the liquid crystal cell is regulated either manually or from an optical sensor, especially this optical-electrical transducer. The purpose of these filter arrangements is to attain as unvarying as possible an illumination intensity for the eye, while the illumination of the object is exposed to considerable fluctuations.
These and similar filter arrangements have great drawbacks in practical use. In practice it is especially desirable to control the quality of the welding flame, i.e. its light and color. A device which tends to do that, to balance variations of intensity in general, does not allow control of corresponding quality features of the welding flame, and especially the experienced welder gauges from the intensity of the welding flame the appropriate suitable temperature and/or the constancy of the flame arc length for the operation.
Other drawbacks of known devices exist in that light disturbance, e.g. the flickering of lamps or any optional intensity differences in the surrounding light, is likewise picked up and compensated by suitable dimming of the light shield. Thereby the gauging of the flame quality is considerably hampered if not made altogether impossible.
Other sources of interference or malfunction are to be seen in all of the devices which produce non-optical, electrical, magnetic or electromagnetic alternating fields in the wave length range of detectable visible light, as these fields too may be emitted from halogen- or fluorescent-tubes. In particular, high current- and voltage-producing welding machines as used for welding prove to be notable sources of interference.
Another problem with the use of the known filter arrangements exists in that these arrangements are dimmed only when variation of intensity is detected as it occurs during high frequency welding.
However, it is precisely the goal of the manufacturer of modern welding apparatus to be able to produce as quiet as possible and increasingly smaller welding flames. Thus, traditional filter arrangements are no longer suitable in an overall sense to fulfill legally prescribed glare protection regulations.
With the foregoing and other objects, advantages and features of the invention that will become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims and to the several views illustrated in the drawings.